The emergence of organic-inorganic perovskites has opened up new opportunities for photovoltaics and novel fundamental aspects of light-matter interaction. In this PhD project, the student will harvest the potential of this emerging family of materials to explore strong light-matter interaction in quantum cavity electrodynamics, exciton-polariton coupling and single-photon emission. This fundamental knowledge will then serve as a launching pad for pioneering electrically driven perovskite-based light sources with the broad tunability of emission wavelengths in the spectral range from ultra-violet (UV) to near infra-red (IR) -such as perovskite lasers via photonic or polaritonic lasing, and microcavity-enhanced single-photon devices.

Optically active organic and inorganic perovskites are materials with composition ABX3(A = CH3NH3+, Cs; B = Pb2+or Sn2+; and X = Cl−, I−, and/or Br−). They have been shown to exhibit very high power conversion efficiencies, they are low cost, nature-abundant in their raw form, and their fabrication processes are low-temperature and scalable. These unique properties make perovskites uniquely suited for revolutionary photovoltaic and lighting applications. For example, solution-processed colloidal perovskites have been shown to display a near-unity photoluminescence quantum yield [1], which is comparable to the values demonstrated with epitaxially grown gain media in extensively used III-V laser diodes. However, the gateway to novel opto-electronic applications would only come from the demonstration of electrically driven lasing which is yet to come.

Understanding the strong luminescence emission of perovskite materials will be the essential starting point of this ambitious PhD project. For example, the nature of the room temperature emission of the typical methylammonium lead iodide perovskite remains controversial with possible interpretations pointing to free carrier recombination, direct-indirect transition or excitonic emission. Distinct from the conventional semiconductors, quantum confinement and reduced dielectric screening in atomically thin perovskites (2D or quasi-2D) remarkably enhance quasiparticle interactions where many-body effects become more obvious. The optical transitions may entangle with high-order excitonic quasiparticles such as trions and biexcitons and cause unconventional excitonic emission, which will be studied in this PhD project. The final goal of this project will be to demonstrate an electrically driven hybrid graphene/perovskite laser. To accomplish this ambitious aim, the student will harvest the unique synergy of state-of-the-art techniques and complementary knowledge by Dr Namphung Peimyoo (NP) on atomically thin light emitting diodes [2] and lasers [3] and the novel atomically thin electrically conductive graphene materials known as graphExeter [4] discovered by the team of Prof Craciun and Prof Russo.

This project aligns with three themes of the metamaterials CDT: a) Graphene and other 2D Materials, b) Nanomaterials and nanocomposites, and c) Quantum Metamaterials. The student in this project will benefit from the broad range of activities on metamaterials at the Exeter CDT. In particular, the top-notch training offered to CDT students will complement the technical skills acquired in the project and diversify the student’s strengths in view of a career in academia or in the industrial sector.